The present disclosure relates to the field of display technology, and more particularly to an active matrix organic light-emitting diode (AMOLED) pixel driving circuit and a pixel driving method.
Organic light emitting display (OLED) devices have become the display devices having the highest developmental potential due their advantages, such as self-illumination, low driving voltage, high illumination efficiency, short response period, high definition and high contrast, nearly 180 degree viewing angle, wide operating temperatures, flexible display, a large full-color display area, etc.
Conventional AMOLED pixel driving circuits are always 2T1C, which means being composed of two thin film transistors and one capacitor, for changing voltage into current.
Please refer to FIG. 1, the present AMOLED pixel driving circuit with a 2T1C structure comprises a first thin film transistor T10, a second thin film transistor T20, a capacitor C10, and an OLED D10. The first thin film transistor T10 is a driving thin film transistor, the second thin film transistor T20 is a switching thin film transistor, and the capacitor C10 is a storage capacitor. More specifically, a gate of the second thin film transistor T 20 receives a scanning signal Gate, a source of the second thin film transistor T 20 receives a data signal Data, and a drain of the second thin film transistor T 20 couples to a gate of the first thin film transistor T10. A source of the first thin film transistor T10 receives a positive voltage OVDD of a power source, a drain of the first thin film transistor T 10 couples to an anode of the OLED D10. The cathode of the OLED D10 receives a negative voltage OVSS of a power source. One side of the capacitor C10 couples to a gate of the first thin film transistor T10, another side of the capacitor C10 couples to a source of the first thin film transistor T10. While the 2T1C pixel driving circuit drives the AMOLED, the current flowing through the OLED D10 meets the following condition:I=k×(Vgs−Vth)2,
where I represents a current flowing through the OLED D10, k represents an intrinsic conductive factor of the driving thin film transistor, Vgs represents the voltage difference between a gate and a source of the first thin film transistor T10, and Vth represents the threshold voltage of the first thin film transistor T10. Therefore, it can be seen that the current flowing through the OLED D10 relates to the threshold voltage for driving thin film transistors.
The threshold voltages for the driving the thin film transistors in each of the pixel driving circuits vary due to instability resulting from the manufacturing processes of panels. Therefore, the currents flowing into OLEDs will be different, even when the same data voltage on the driving thin film transistors is applied to each of the pixel driving circuits. As a result, consistency and image display quality will be affected. Once the driving duration becomes longer, materials of thin film transistor begin deteriorating and varying, then the threshold voltage for driving the thin film transistor will drift. Also, drifting variations of the threshold voltages of each of the driving thin film transistors are different due to deteriorating diversity of the materials. Those foregoing occasions leads to issues such as unevenness in the display, increase in starting voltage for driving the thin film transistors, decrease of the current flowing through the OLED, decline in luminosity, and decline of illuminating efficiency.
Therefore, an AMOLED pixel driving circuit and method is required to solve the problems of the present technology.